The objectives of this phase II SBIR contract are the production by the synthetic peptide procedure of specific, non-crossreacting monoclonal antibodies to the tumor antigens (T-antigens) of the human papovaviruses JC and BK. These antibodies will then be developed into useful research reagents. These human viruses produce tumors in animals, but their possible role in human neoplasms is not known. The reagents to be developed under this SBIR contract shall help researchers delineate this role, if it exists, and do basic studies on the viral transformation of cells. Specifically, the contractor shall produce specific, non- crossreactive monoclonal antibodies to JC virus large T-antigen, JC virus small T-antigen, and BK virus large T-antigen, and BK virus small T-antigen with priority given to the two large T- antigens. The monoclonal antibodies should not be crossreactive with each other or with SV40 T-antigens. The use of ten well selected peptides should be sufficient to generate the required monoclonal antibodies.